This application claims benefit of Japanese Application No. 2000-339477 filed in Japan on Nov. 7, 2000, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a multi-display device, or more particularly, to a multi-display device that combines partial images projected from a plurality of projectors so as to construct one image.
2. Description of the Related Art
In the past, various proposals have been made concerning a multi-display device that combines partial images projected from a plurality of projectors so as to construct one image.
As for such a multi-display device, for example, Japanese Patent Unexamined Publication No. 9-211386 has disclosed a projection system that projects a synthetic image by overlapping a first image and a second image in a superposed-portion area on a screen. The projector system has a first light bulb projector and a second light bulb projector. Each projector includes a light source, a light bulb, a condenser, and a projection lens. The light bulb reflects or transmits image light. The condenser directs light emanating from the light source to the light bulb. The projection system further includes a uniting means that is located on a light path linking the light bulb and the projection lens, the light source and the condenser, or the photography lens and the screen. The uniting means smoothes a difference between light levels attained in the superposed-portion area when the light bulb is on and when it is off without lowering a contrast ratio offered by the first or the second light bulb projector. Thus, a seam in an image can be nullified but the contrast ratio will not be lowered.
Moreover, Japanese Patent Unexamined Publication No. 3-53288 describes a multi-video projector composed of a plurality of video projectors each of which includes at least an image projection unit and a screen. The multi-video projector has a partition panel interposed between the image projection unit and the screen. The partition panel has the ability to intercept the whole or part of the image projection light, which is not included in prisms defined by an effective image field on the screen and an intersection between an exit pupil of the projection lens and the ray axis of the emitted light.
Moreover, Japanese Patent Unexamined Publication No. 3-53288 describes a multi-video projector composed of a plurality of video projectors each of which includes at least an image projection unit and a screen. The multi-video projector has a partition panel interposed between the image projection unit and the screen. The partition panel has the ability to intercept the whole or part of the image projection light, which is not included in prisms defined by an effective image field on the screen and an intersection between an exit pupil of the projection lens and the ray axis of the emitted light.
Furthermore, Japanese Patent Unexamined Publication No. 6-169444 describes a video multi-image projection system that simultaneously projects a plurality of images on a screen. When adjoining images are projected to overlap each other, the superposed portion of the overlapping images is transmitted through either of a half mirror, a translucent white member, or a translucent black member. The transmittance rate of the overlapping images ranges from 35% to 45%.
Patent Cooperation Treaty Publication No. WO95/25292 describes an image projecting apparatus in which each projector has a lamp, a condensing optical system, a liquid crystal display panel, a projecting optical system, and one or more comb-like members having substantially triangular teeth. The condensing optical system condenses and radiates the light emanating from the lamp. The liquid crystal display panel receives light radiated from the lamp through the converging optical system and displays an image. The projecting optical system projects an optical image displayed on the liquid crystal display panel. The image projecting apparatus is positioned so that the teeth of the mask member will intercept the marginal part of the light propagated from the liquid crystal display panel to the projecting optical system. Owing to the teeth of the mask member, a light level attenuates towards the margin of the superposed portion of projected overlapping images. Thus, partial images are synthesized smoothly. According to the disclosed technology, the comb-like mask member is intended to control a light attenuation curve, which indicates a change in light level due to attenuation occurring in the superposed portion of partial images.
A known technology for improving the homogeneity of a projected screen images that is implemented in a light source included in a multi-display device having a plurality of projectors like the ones mentioned above will be described with reference to FIG. 3A to FIG. 3F.
A dot-like light source shown in FIG. 3D is adopted as a light source to be included in a projector. An illumination device 11 having such a dot-like light source may be used to illuminate a display device 16. In this case, the display device is, as shown in FIG. 3E, illuminated with a dot-like light source image alone. At this time, as shown in FIG. 3F, the luminance in the center of a radiated surface tends to get higher than the one in the surrounding portion thereof.
As far as a multi-display device including a plurality of projectors is concerned, partial images projected by the projectors are joined in order to construct one image. It is therefore especially important that the luminance in each partial image is uniform.
As shown in FIG. 3A, light emanating from the illumination device 11 is passed through a first lattice-like (dot-matrix-like) lens array 12 and a second lattice-like (dot-matrix-like) lens array 13. Thus, a plurality of secondary light source images arrayed on a planar basis (or more particularly, in the form of a lattice-like matrix) is produced as shown in FIG. 3B.
Consequently, as shown in FIG. 3C, the display screen of the display device 16 is illuminated nearly uniformly so that uniform brightness will be observed all over the display screen.
On the other hand, in the aforesaid multi-display device having a plurality of projectors, partial images are projected so that adjoining partial images will overlap to have their margins superposed on each other. A sheet interceptor is used therefore to intercept luminous flux that is projected at an area of superposed portion on the screen and that represents partial images. This is intended to prevent the luminance in superposed portion of adjoining images from getting higher. Consequently, when a portion of the partial image is superposed on a portion of an adjoining partial image, the superposed portion exhibits the same luminance as the other portions of the partial images that are not superposed on each other.
In the foregoing configuration, when a plurality of light sources like the aforesaid one (or a plurality of secondary light source images) are used to illuminate a display device, one sheet interceptor provides a plurality of shadows. Consequently, a stepwise distribution of luminance values occurs in the margin of a partial image projected on the screen by each projector.
FIG. 28 shows a stepwise distribution of luminance values on the screen which occurs when a sheet interceptor is used to intercept light radiated as a plurality of secondary light source images.
As shown in FIG. 28, when light radiated as a plurality of secondary light source images 18a is partly intercepted by a sheet interceptor 95, a border between an intercepted area on the screen 3 and a non-intercepted area thereon varies depending on the position of each secondary light image 18a. This results in a belt-shaped distribution of luminance values 96 that is a stepwise difference in luminance.
Furthermore, when a double-plate projector that divides the path of illumination light into portions associated with colors and that illuminates display devices associated with the colors is adopted, the marginal part of the projected light may suffer color disjunction. This is attributable to a difference in the optical length or a shift of an exit pupil dependent on a wavelength. When the marginal part of light that is suffering from the color disjunction is intercepted by an intercepting member, a light level observed on the screen differs from color to color. Consequently, the margin of a partial image projected from the projector suffers coloring.
What is described in the Patent Cooperation Treaty Publication No. WO95/25292 has something like the teeth of a comb formed for the purpose of reducing the light level of the marginal part. No description is made as to how to overcome a stepwise change in luminance derived from a plurality of light sources or a plurality of secondary light source images or coloring.
Consequently, when a plurality of light sources or a plurality of secondary light source images are used for illumination, a technology for alleviating the stepwise change in luminance or the coloring is desired in order to attain higher image quality.
Accordingly, an object of the present invention is to provide a multi-display device that alleviates a stepwise change in luminance or coloring caused by the shadow of the intercepting edge of an intercepting means which is derived from employment of a plurality of light sources or secondary light source images. Consequently, the multi-display device projects a higher-quality image.
In order to accomplish the above object, according to the present invention, there is provided a multi-display device having a plurality of projectors each of which projects a partial image on a screen so that the partial image and an adjoining partial image will overlap to have their margins superposed on each other. The plurality of partial images are synthesized to construct one image. Each projector consists mainly of an illuminating means, a display means, and a projecting optical system. The illuminating means radiates light using a plurality of light sources or secondary light source images arrayed two-dimensionally. The display means displays the partial images while being illuminated with light radiated from the illuminating means. The projecting optical system projects luminous flux representing the partial images displayed on the display means on the screen.
Moreover, the multi-display device includes an intercepting means. The intercepting means intercepts the marginal part of luminous flux that represents a partial image, and lowers the luminance in a portion of the partial image to be superposed on a portion of an adjoining partial image so that the luminance in the superposed portion of the partial images will be substantially identical to the luminance in the other portions thereof. The intercepting edge of the intercepting means has a plurality of continuous or discontinuous parts that are not parallel to the direction of rows of the plurality of light sources or secondary light source images.
Using the multi-display device in accordance with the present invention, the intercepting edge of the intercepting means has the plurality of continuous or discontinuous parts that are not parallel to the direction of the rows of the plurality of light sources or secondary light source images. Consequently, a stepwise difference in luminance caused by the shadow of the intercepting edge of the intercepting means can be alleviated, and a higher-quality image can be projected.
Moreover, according to the present invention, there is provided a multi-display device having a plurality of projectors each of which projects a partial image on a screen so that the partial image and an adjoining partial image will overlap to have their margins superposed on each other. The plurality of partial images are synthesized to construct one image. Each projector consists mainly of an illuminating means, a splitting means, red, green, and blue color display means, a luminous flux synthesizing means, and a projecting optical system. The illuminating means radiates light using a plurality of light sources or secondary light source images arrayed two-dimensionally. The splitting means splits light emanating from the illuminating means into three color light rays of red, green, and blue. The red, green, and blue color display means are illuminated with the light rays of red, green, and blue propagated from the splitting means, and display the partial images of red, green, and blue. The luminous flux synthesizing means synthesizes polarized light rays representing the partial images of red, green, and blue displayed on the red, green, and blue color display means. The projecting optical system projects light emanating from the luminous flux synthesizing means on the screen.
Moreover, the multi-display device includes an intercepting means. The intercepting means intercepts the marginal part of light representing a partial image on a light path linking the luminous flux synthesizing means and the screen. The intercepting means lowers the luminance in the portion of the partial image to be superposed on that of an adjoining partial image so that the luminance in the superposed portion of the partial images will be substantially identical to the luminance in the other portions thereof that are not superposed on each other. The intercepting means has a sheet polarizer. The sheet polarizer is placed so that an axis of polarization thereof will intersect a direction of polarization of an unnecessary color component ray, whereby color disjunction occurring in the margin of the partial image is corrected.
Using the multi-display device in accordance with the present invention, the intercepting means includes the sheet polarizer placed so that the axis of polarization thereof will intersect the direction of polarization of an unnecessary color component ray. Consequently, stepwise coloring caused by the shadow of the intercepting edge of the intercepting means can be alleviated, and a higher-quality image can be projected.
Furthermore, according to the present invention, there is provided a multi-display device having a plurality of projectors. Each projector projects a partial image on a screen so that the partial image and an adjoining partial image will overlap to have their margins superposed on each other. A plurality of partial images are synthesized to construct one image. Each projector consists mainly of an illuminating means, a splitting means, red, green, and blue color display means, a luminous flux synthesizing means, and a projecting optical system. The illuminating means radiates light using a plurality of light sources or secondary light source images arrayed two-dimensionally. The splitting means splits light radiated from the illuminating means into three color light rays of red, green, and blue. The red, green, and blue color display means are illuminated with the light rays or red, green, and blue propagated from the splitting means, and display the partial images of red, green, and blue. The luminous flux synthesizing means synthesizes the luminous flux representing the partial images of red, green, and blue displayed on the red, green, and blue color display means. The projecting optical system projects light propagated from the luminous flux synthesizing means on the screen.
Moreover, the multi-display device means intercepts the marginal part of the luminous flux representing a partial image on a light path linking the luminous flux synthesizing means and the screen. The intercepting means lowers the luminance in the portion of the partial image to be superposed on that of an adjoining partial image, so that the luminance in the superposed portion of the partial images will be substantially identical to the luminance in the other portions that are not superposed on each other.
The partial image is divided into a sub-partial image having one of the three colors of red, green, and blue and a sub-partial image having the other two colors. When the sub-partial images are disjoined, first color disjunction relevant to the one color and second color disjunction relevant to the two colors occur in the margins of the partial image.
Among the aforesaid plurality of projectors, adjoining projectors share the same superposed-portion area on the screen. One of the adjoining projectors projects a portion of a partial image suffering the first color disjunction at the superposed-portion area, and the other projector projects a portion of a partial image suffering the second color disjunction at the same superposed-portion area. Thus, the color disjunctions are canceled out in the superposed portion area.
Using the multi-display device in accordance with the present invention, the plurality of projectors are arranged so that one of the adjoining projectors that share the same superposed-portion area on the screen will project light that is suffering from the first color disjunction at the superposed-portion area, and the other projector will project light that is suffering from the second color disjunction at the superposed portion area. Thus, the color disjunctions are canceled out in the superposed-portion area. Consequently, stepwise coloring caused by the shadow of the intercepting edge of the intercepting means is alleviated, and a higher-quality image is projected.